The invention relates to a profiled fuel cell flow plate gasket.
A fuel cell is an electrochemical device that converts chemical energy produced by a reaction directly into electrical energy. For example, one type of fuel cell includes a proton exchange membrane (PEM), a membrane that may permit only protons to pass between an anode and a cathode of the fuel cell. At the anode, diatomic hydrogen (a fuel) is oxidized to produce hydrogen protons that pass through the PEM. The electrons produced by this oxidation travel through circuitry that is external to the fuel cell to form an electrical current. At the cathode, oxygen is reduced and reacts with the hydrogen protons to form water. The anodic and cathodic reactions may be described by the following equations:
H2xe2x86x922 H++2exe2x88x92at the anode of the cell, and
O2+4 H++4exe2x88x92xe2x86x922H2O at the cathode of the cell.
Because a single fuel cell typically produces a relatively small voltage (around 1 volt, for example), several serially connected fuel cells may be formed out of an arrangement called a fuel cell stack to produce a higher voltage. The fuel cell stack may include different flow plates that are stacked one on top of the other in the appropriate order, and each plate may be associated with more than one fuel cell of the stack. The plates may be made from a graphite composite or metal material and may include various flow channels and orifices to, as examples, route the above-described reactants and products through the fuel cell stack. Several PEMs (each one being associated with a particular fuel cell) may be dispersed throughout the stack between the anodes and cathodes of the different fuel cells. The anode and the cathode may each be made out of an electrically conductive gas diffusion material, such as a carbon cloth or paper material, for example.
Referring to FIG. 1, as an example, a fuel cell stack 10 may be formed out of repeating units called plate modules 12. In this manner, each plate module 12 includes a set of composite plates that may form several fuel cells. For example, for the arrangement depicted in FIG. 1, an exemplary plate module 12a may be formed from a cathode cooler plate 14, a bipolar plate 16, an anode cooler plate 18, a cathode cooler plate 20, a bipolar plate 22 and an anode cooler plate 24 that are stacked from bottom to top in the listed order. The cooler plate functions as a heat exchanger by communicating a coolant through flow channels in either the upper or lower surface of the cooler plate to remove heat from the stack 10. The surface of the cooler plate that is not used to communicate the coolant includes flow channels to communicate either hydrogen (for the anode cooler plates 18 and 24) or oxygen (for the cathode cooler plates 14 and 20) to an associated fuel cell. The bipolar plates 16 and 22 include flow channels on one surface to communicate hydrogen to the membrane of an associated fuel cell and flow channels on the opposing surface to communicate oxygen to the membrane of another associated fuel cell. Due to this arrangement, each fuel cell may be formed in part from one bipolar plate and one cooler plate, as an example.
For example, one fuel cell of the plate module 12a may include an anode-membrane-cathode sandwich, called a membrane-electrode-assembly (MEA), that is located between the anode cooler plate 24 and the bipolar plate 22. In this manner, the upper surface of the bipolar plate 22 includes flow channels to route oxygen near the cathode of the MEA, and the lower surface of the anode cooler plate 24 includes flow channels to route hydrogen near the anode of the MEA.
As another example, another fuel cell of the plate module 12a may be formed from another MEA that is located between the bipolar plate 22 and the cathode cooler plate 20. The lower surface of the bipolar plate 22 includes flow channels to route hydrogen near the anode of the MEA, and the upper surface of the cathode cooler plate 24 includes flow channels to route oxygen near the cathode of the MEA. The other fuel cells of the plate module 12a may be formed in a similar manner.
To communicate the hydrogen, oxygen and coolant throughout the stack, each plate includes several openings that align with corresponding openings in the other plates to form passageways of a manifold. The fuel cell stack typically includes flow plate gaskets that reside between the plates to seal off the various manifold passageways and flow channels. For example, such a flow plate gasket may be located between the anode cooler 24 and the bipolar plate 22 and reside in a gasket groove of the bipolar plate 22, for example. The flow plate gasket may be an O-ring gasket that has a disk-shaped cross-section when uncompressed.
The seals that are provided by the flow plate gaskets may govern the lifetime of the fuel cell stack. For example, a coolant may be used that is incompatible with the membrane and thus, may damage the membrane on contact. Therefore, if a particular flow plate gasket is not compatible with the coolant, the coolant may permit the coolant to enter one of the reactant manifold passageways and contact the membrane, an event that may cause the corresponding fuel cell to fail. Unfortunately, the failure of a fuel cell may prompt a shut down of the entire fuel cell stack until repairs may be made.
Thus, there is a continuing need for fuel cell flow plate gaskets that have improved sealing capabilities.
In one embodiment of the invention, a flow plate gasket that is usable with a first fuel cell plate and a second fuel cell plate includes a material that is adapted to form a seal between the first and second fuel cell plates. The material includes at least two spaced ridges to contact the first fuel cell plate when the gasket is compressed between the first and second fuel cell plates.
In another embodiment of the invention, an assembly includes a first fuel cell plate, a second fuel cell plate and a gasket. The gasket is adapted to form a seal between the first and second fuel cell plates. The gasket includes at least two spaced ridges to contact the first fuel cell plate when the gasket is compressed between the first and second fuel cell plates. In general, advantageous features of embodiments of the present invention may include: seals having higher void volume for improved compression than traditional o-ring seals that are placed in rectangular grooves; seals having an increased number of sealing surfaces than o-ring configurations; seals that can more accurately and reliably be placed into position during fuel cell stack assembly; and seals that provide less movement during compression, such as the twisting and other movement of o-rings that may occur during compression.
Advantages and other features of the invention will become apparent from the following description, from the drawing and from the claims.